Method of road construction

ABSTRACT

A method of stabilization of earth material to a controlled depth to form a roadway base material or subgrade, the method consisting of cutting and comminuting native or prepared earth material to an automatically controlled depth whereupon cut material is spread to an automatically controlled thickness above the controlled depth line to form an even layer of the comminuted material for utilization as a roadway base capable of receiving and supporting paving material thereupon. Depending upon the suitability of the earth material for base purposes, additional steps may be taken to add specified liquid or dry materials to the comminuted earth material to adjust the plasticity index to a proper value for utilization as a paving material support substance.

United States Patent [72] Inventor George W. Swisher, .Ir. 2,902,9089/1959 Schiavi 94/39 Oklahoma City, Okla. 3,224,347 12/1965 Seaman 94/40[21] Appl. No. 796,853 3,418,901 12/1968 Hanson 94/39 [22] Filed Feb. 5,1969 3,423,859 1/1969 Swisher 37/108 [45] Patented Aug. 10, 19713,435,546 4/1969 lverson 37/108 (73] Assignee CM] Corporation 3,452,4617/1969 Hanson 94/40 X Oklahoma City Okla Primary ExaminerNile C. Byers,Jr.

AuorneyDunlap, Laney, l-lessin and Dougherty [54] METHOD OF ROADCONSTRUCTION 9 ABSTRACT: A method of stabilization of earth material toa [52] US. Cl 94/22, controlled depth to form a roadway base material orsubgrade, 9 the method consisting of cutting and comminuting native or[5] Int. Cl E01: 21/00 prepared earth material to an automaticallycontrolled depth [50] Field of Search ..94/40, 39.5, whereupon cutmaterial is spread to an automatically con- 3951. 108 trolled thicknessabove the controlled depth line to form an even layer of the comminutedmaterial for utilization as a [561 References cud roadway base capableof receiving and supporting paving UNITED STATES A T material thereupon.Depending upon the suitability of the 1,269,098 6/1918 Latta 94/39 earthmaterial for base purposes, additional steps may be 1,632,969 6/1927Homer 94/39 taken to add specified liquid or dry materials to the com-1,953,890 4/1934 Allen 94/39 minuted earth material to adjust theplasticity index to a 2,128,273 8/1938 Stevens 280/6 proper value forutilization as a paving material support sub- 2,20l,493 5/1940 Jorgensen94/40 stance.

l W x 492 I "l I l I l l ,5; ll f i- Md :4

METHOD OF ROAD CONSTRUCTION BACKGROUND OF THE INVENTION 1. Field oftheInvention The invention relates generally to a method of roadwayconstruction and, more particularly, but not by way of limitation, itrelates to an improved method of forming a roadway base to a controlleddepth for deposition of earth material cut and processed in situ.

2. Description of the Prior Art The prior art includes various teachingsdirected to utilization of native or other earth material in formingsupport structure for overlay of roadway surfaces. Prior attempts at inplace" stabilization were characterized by an inability to maintainreliably a specified depth or base line and, therefore, a properthickness of the stabilized base layer; and, deleterious effects tofinished roadways containing such base layer have necessitated outlawingof such practices in many states. That is, earth material may have beencut, ground and whatever for placement as base material and then leveledoff to a neat line to form the base layer; however, the prior methodsallowed no way whereby it could be ascertained that the base layer wasuniform in thickness, i.e. the roadway bottom or base line was not cutto a controlled level or depth.

SUMMARY OF THE INVENTION The present invention contemplates a method ofroad construction utilizing native or prepared earth material for basematerial wherein the earth material is cut, comminuted and layeredautomatically at a controlled depth and having a controlled thickness.In a more limited aspect, the invention consists of cutting the earthmaterial to a predetermined base line as automatically controlled from apreselected external reference line, and comminuting the earth materialto a desired consistency or maximum particle size for placement on thecut roadway above the base line to a desired thickness also controlledfrom the reference line. It is further contemplated to injectstabilizing additives, either liquid or dry in form, to the cut earthmaterial for mixture therewith to adjust the stabilization propertiessuch that the stabilized base is optimally processed to receiveadditional roadway material for support thereon.

Therefore, it is an object of the present invention to provide a methodfor building roadways from the base structure upward while utilizingnative earth materials for stabilization.

It is also an object of the invention to provide a method of formingroadway base structure from earth material wherein each interface of thebase structure is automatically formed at a controlled depth.

It is a further object of the invention to enable utilization of nativeearth material in forming reliable, controlled depth roadway base wherethe physical characteristics of the native earth material will permit.

Finally, it is an object of the present invention to provide a method ofroadway construction which enables great economy with little or noreduction in strength and reliability of roadways.

Other objects and advantages of the invention will be evident from thefollowing detailed description when read in conjunction with theaccompanying drawings which illustrate the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 depicts a section of earth surfacewith a layer of cut native earth material as might be formed byconventional roadbuilding machinery utilized for grade cutting;

FIG. 2 depicts a section of paved roadway formed along the same earthsection as shown in FIG. 1;

FIG. 3 depicts a section of earth surface having a cut and comminutednative material base layer formed thereon to a controlled depth andthickness in accordance with the present invention;

FIG. 4 is a partial block diagram of apparatus which may be utilized incarrying out controlled depth stabilization in situ in accordance withthe present invention;

FIG. 5 is a side elevation of one form of apparatus which may beutilized in carrying out the method of the invention;

FIG. 6 is a front view of the apparatus shown in FIG. 5;

FIG. 7 is an enlarged, front elevation of a cutter as may be utilized inthe apparatus of FIGS. 5 and 6;

FIG. 8 is a section of the cutter as taken along lines 8-8 of FIG. 7;and

FIG. 9 is a front view of roadbuilding apparatus similar to that ofFIGS. 5 and 6 but being adapted for single-land usage with increasedcutter speed.

DETAILED DESCRIPTION OF THE INVENTION The method of the presentinvention enables construction of roadway utilizing native or preparedearth materials in situ as base support layer, and the method bringsreliability to such practice through the employ of automated profileroadbuilding techniques. That is, recent advances in automated profileroadbuilding is based upon the premise that you build a roadway from thebottom up and not from the top down as has been done since early days ofroad construction with less than desirable results. Such latter daytechniques have been brought about primarily through the capabilities ofrecent construction equipment innovations as best exemplified by theteachings of US Pat. application Ser. No. 446,239 entitled RoadConstruction Method and Apparatus and filed on Apr. 7, I965 in the nameof George W. Swisher et al., now US. Pat. No. 3,423,859, and copendingUS. Pat. application Ser. No. 749,823 entitled Control Systems for RoadConstruction Machinery filed on Aug. 2, I968 in the name of George W.Swisher, .lr., et al.

The prior attempts at utilization of native earth material for placementin situ as roadway base layer was generally unreliable due to aninability to maintain a uniform depth after compaction of the base layeralong a right-of-way. FIG. 1 depicts such a prior attempt to rearrangeearth material in situ. Gradecutting machinery I0, such as conventionalbulldozers, motorgraders, and various other cutting and loadingmachinery, might be utilized in one or more units to remove native earthmaterial from the earth 12 having a surface 14. The gradecuttingmachinery 10 would attempt to move a certain top depth of the earth 12to redeposit loosened or broken up earth material 16 along theright-of-way. While the grade-cutting machinery 10 could continually cutdown to a base line 18, there has been no known practice whereby thebase line 18 could be maintained uniformly level to the roadway neatline such that it would also insure uniformity of base layer 16 whencompacted thereon. For example then, when the base line 18 experiencesan undulation peak 20 the base layer 16 in the area 22 would, ofnecessity, constitute a thinner layer since the upper surface 24 of thebase layer I6 will be compacted and smoothed to the roadway neat line.

FIG. 2 shows the manner in which a faulty section of finished roadwaymight result from the attempt at in place stabilization or utilizationof native earth material as depicted in FIG. I. The base layer 16 willhave been smoothed and compacted such that upper surface 24 will equalthe grade neat line; thereafter, a suitable form of base material 26might be deposited in uniform layer and/or a paving material slab 28will next be supported to provide the roadway surface. The employ ofbase 26, e.g. bituminous aggregate or other wellknown base material, aswell as the thicknesses of base 26 and paving material 28 will vary withthe exigencies of different applications as well as requirements ofbuilding specifications in the locale.

In any event, core samples taken at spaced intervals along the roadwayas depicted in FIG. 2 will show variations in the base layer 16, some ofwhich can be extremely detrimental to roadwear and the ability towithstand normal temperature changes. A core sample taken at area 22,shown by dash lines 30, will show that the base layer 16 is of much lessthickness than the same base layer 16 as sampled by a core taken alongdash lines 32.

As shown in FIG. 3, the method of the present invention enablesutilization of earth material as a stable base layer which can beuniformly extruded along a right-of-way having an automaticallycontrolled depth. Thus, a suitable form of cutting and comminutingmachinery 32 is moved along a surface 14 of earth 12 to cut andcomminute the native earth material for deposition in a base layer 34 ofuniform thickness and density. The stabilization properties of thenative earth material may be adjusted to provide best function as apavement base layer. Thus, it may be desirable to adjust the plasticityindex, i.e. the difference in moisture content of soil between theliquid and plastic limits as expressed in percentage, so that the basecapabilities may be altered to an optimum value. A suitable stabilizermaterial 35, eg lime, water, oil, and other well-known additives, may beinterjected into cutting and comminuting machinery 32 for thoroughmixture throughout the native earth material prior to its beingdeposited as uniformly thick base layer 34.

Automated profile control is maintained over the cutting and comminutingmachinery 32 such that it cuts down to a uniform base line 36 which iscontinually maintained at a uniform distance from some externalreference, thus, controlled depth as will be further described below.Similarly, the cutting and comminuting machinery 32 has the capabilityof leaving the base surface 38 at a uniform distance above the base line36, it too being controlled from the external reference source. Suchautomatic profile control enables the guidance and cutting depth controlof the cutting and comminuting machinery 32 to deposit base layer 34 ofnative earth material along the right-of-way. Such automatic profilecontrol is the particular subject matter of the aforementioned Pat.applications, U.S. Ser. Nos. 446,239 (now U.S. Pat. No. 3,423,859) and749,823. While description is directed more to the techniques ofutilizing the native earth material, it should be understood that thepresent method is equally applicable to controlled depth cutting withpreparation of imported or prepared base material. The use of nativematerial is desirable for obvious reasons, but not always possible forobtaining required results.

Referring now to FIG. 4, the apparatus 40 exemplifies a form of deviceor mechanical structure which is suitable for carrying out the method ofthe invention. The apparatus 40 may consist of a frame 42, of suitableshape as necessitated by design requirements, which is movably supportedon forward mobile support means 44 and rearward mobile support means 46.The respective support means 44 and 46 are connected via extendablesupport members 48 and 50, respectively, to the frame 42, and each ofextendable support members 48 and 50 is operative under the control ofrespective height controls 52 and 54. Height controls 52 and 54 areindividually controlled from respective height sensors 56 and 58 whichderive height or level indication from an external reference, in thiscase, a stringline 60. Level sensing of stringline 60 for inputtocontrol the respective height control sensors 56 and 58 may be byvarious well-known means such as are described in the aforementioned US.Pat. applications Ser. Nos. 446,239 and 749,823; and such controis arethe particular subject matter of a U.S. Pat. application Ser. No.683,256 entitled Line Tracer Control Device" filed Nov. 15, 1967 in thename of Steele et al.

The frame 42 may then carry a succession of operating elements such as arotary cutter 62. The rotary cutter 62 may consist of a rotating shaft64 carrying a plurality of cutter arms 66, each of which supports acutter tooth 68 on the end thereof. The rotary cutter 62 is supportedfrom a support member 70 which is adjustably connected to a cuttersupport 72 supported by the main frame 42. A suitable reservoir orstorage tank may be secured to the main frame 42 for the purpose ofholding stabilizer material for injection via a suitablinput conduit 76into the general area of comminution abmr rotary cutter 62. A mold board78 is suspended from a mold board support 80 which is adjustably affixedto the main frame 42. Similarly, a rotary distributing auger 82 issupported from an elongatable support member 84 which is suspended fromframe 42 by means of an auger support 86, and a rear moldboard support88 extends rear moldboard 90 downward to the rear of rotary auger 82.

The frame 42 has its level adjusted in response to height controlsensors 56 and 58 which control the operations of height controls 52 and54 to vary the elongation of the respective support members 48 and 50.Each of the rotary cutters 62, moldboard 78, auger 82 and rear moldboard90 is individually adjustable as to depth of operation below frame 40 bythe adjustment of their respective cutter support '72, moldboard support80, auger support 86 and rear moldboard support 88. For an initialsetting of the relative displacement of the operating elements, i.e. thesetting of rotary cutter 62 at a preset depth and with moldboard 78,rotary auger 82 and moldboard 90 relatively displaced at a higher level,the frame 42 may be moved along the right-of-way with support members 44and 48 set at a level which is determined in relation to the stringline60. Continual adjustment of the level of frame 42 relative to stringline60 also serves to adjust the depth of cutting at base line 36 as well asthe base surface 38 which is displaced a predetermined distancethereabove.

One form of automatic profile machinery which is suitable for employ incarrying out a stabilization in situ method as disclosed herein is shownin FIG. 5. This apparatus is similar to that disclosed in theaforementioned U.S. Pat. application Ser. No. 446,239 with the exceptionthat the rotary cutter is altered as will be described below. Theconstruction machine is essentially a dual lane automatic grade-cuttingmachinery as disclosed in the prior application; however, alteration ofrotary cutter 102 such that it includes an increased number ofindividual cutter arms 104, each being somewhat longer than theconventional cutter elements, will enable function in accordance withthe method of the present invention. Construction machinery 100 consistsof a main frame 106 which is supported by a pair of forward support legs108 and rearward support legs 110 disposed in quadrature array. Theforward support legs 108 are secured to respective forward verticalsupports 112 which, in turn, are connected to yoke members 114 which areattached for support above mobile track units 116. The rear support legs110 connect to respective rear vertical supports 118 which extend fromyokes 120 and rear mobile track units 122. Forward and rearward steeringis effected through tension bars 124 and 126 in a manner which isdisclosed at length in the aforementioned U.S. Pat. application Ser. No.446,239.

The top surface of main frame 106 serves as an operating platform 128and an operators console 130 is disposed at the forward edge thereofwhile a central power source 132 is supported at the rear. The rotarycutter 102 is supported from cutter support 134 which is verticallymovably supported beneath main frame 106. While various power inputforms may be employed to supply drive to the rotary cutter 102, asuitable form of hydraulic drive is employed which is capable ofproviding continuous control of rotary cutter 102 between 0 and 80 rpm.A moldboard 136 is also vertically adjustably supported beneath mainframe 106 at a position just to the rear of rotary cutter 102 to provideboth baffling and distribution function. A rotary auger 138 is supportedfrom a support member 140 in vertically adjustably manner similar tothat for rotary cutter 102, and a similar hydraulic drive is alsoutilized to provide revolution control. A rear moldboard 142 is thenvertically adjustably supported to the rear of auger 138.

Stabilization material such as lime, water, or other stabilizingcompounds may be retained in storage tanks 144 and 146 which aresuitably secured across the front of the construction machine 100. Thestorage tanks [44 and 146 may include respective control structures 148and 150 for distributing the dried or liquid-stabilizing material acrossthe length of rotary cutter 102. Respective left and right stringlines152 and 154 are also shown as they may be contacted by the varioussteering and level control-sensing devices.

Thus, a right front level control 156 derives indications from a movablesensing arm 158 to control the vertical extension of vertical supportmember 112 relative to stringline 152, the external reference sourcewhich in most cases would be constant to grade line of the right-of-way.A similar sensor (not specifically shown) would be disposed at the rightrear to control vertical extension of vertical support member 118. Onthe left side (right side of FIG. 6), a control device 160 derives levelcontrol indications through position of sensing arm 162 as urged bystringline 154, and steering sensing is derived from a control device164 and sensing arm 166. Similar level and steering control deviceswould be disposed adjacent the left Referring now to FIG. 7, the rotarycutter 102 is shown in greater detail. The cutter 102 consists of aplurality of radially extending cutting members 104. Each of cuttermembers 104 consists of a cutter arm 170 which is welded to and radiallyextending from a central shaft 172. The cutter members 104 in one casemay be arrayed in three intertwined helical flights, and that is thearray as depicted in FIGS. 7 and 8. Thus, noting FIG. 8, the cuttingmembers 104 are arrayed as three equally displaced helical flights asexemplified by particular cutter members 172, 174 and 176 which areattached in coplanar affixture to the center shaft 172. Each cutter arm170 supports a cutter head 180 at its outward end, as has been founddesirable in practice, the cutter heads I80 are so formed that theyreceive removable, hardened steel cutter teeth (not specifically shown)therein.

The rotary cutter 102 is primarily characterized by having an increasednumber of cutter members 104 disposed in greater density therealong sothat cutter 102 has the capability of applying an extremely thoroughchopping or cutting action to earth material as it moves along theright-of-way. In addi tion to the density of cutting members 104, therotary cutter 102 is also controllable over a wide range of rotaryspeeds to enable further adjustment as to the degree and uniformity ofcomminution of the native earth material. With standard rotary controlsystems as present in conventional forms of construction machine 100,the operator may have the capability of controlling rotation of cutter102 between 0 and 80 rpm. Still greater speeds approaching 120 rpm. areattainable when utilizing a single-lane type of machine as shown in FIG.9.

A construction machine 190, another commercially available type ofautomatic grade control machine, is highly similar to the constructionmachine 100 of FIGS. 5 and 6 with the exception that it is built arounda more narrow frame 192 which carries single-lane working or operatingelements. In this case, a rotary cutter 194, which is similar to rotarycutter 102 in tooth structure and density but about one-half as long, isemployed at higher revolutional speeds. This is enabled by apply ingsimilar hydrostatic drive, but greater rotational speeds are realizedsince the two drive systems required by rotary cutter 102 (FIG. 6) areboth applied to control the single-lane rotary cutter 194. It is capableof continuous control between 0 and 120 rpm.

Such speed capability and control enables a most thorough cutting andcomminuting operation of earth material, and this also allows morethorough mixture of stabilizing material throughout the comminuted earthmaterial prior to its deposition or extrusion as the base layer alongthe right-of-way. Stabilizing material may be retained in a suitablestorage tank 196 which is affixed across the forward edge of frame 192and which includes a suitable form of distribution structure I98 forleading stabilizing material down for controlled release into thecomminution area about rotary cutter I94.

In operation, and utilizing various of the apparatus capable ofautomatic profile control earth-working, or controlled depth cutting andcomminution, the construction machinery is first set up relative to anexternal level reference such that the various operating elements aredisposed at a preset depth. Thus, and referring to FIG. 4, stringline 60serves as the external reference line along a right-of-way and thecutter support 72 and support member 70 are adjusted so that rotarycutter 62 will cut to the elevation level of a predetermined base line36 within the earth 12. Similarly, the respective moldboard support 80,auger support 86 and moldboard support 88 are preadjusted so that theywill extend their respective operating elements to a preset levelrelative to reference or stringline 60. The construction machine 40 canthen proceed along a rightof-way cutting and comminuting the portion ofearth material 12 above base line 36 for deposition in situ as a uniformbase layer 34. The base line 36 as well as the upper surface 38 of baselayer 34 is automatically maintained at a controlled depth and thicknessrelative to the stringline 60.

Depending upon the qualities of the native earth material, selectedadditives may be applied, e.g. through storage tanks 74 and injectionline 76, for the purpose of stabilizing the native earth material sothat optimum base characteristics are achieved. For example, it may bedesirable to add dry commercial lime at a certain rate to lower theplasticity index of the native earth material 12 to increase its abilityto support a paving slab and the attendant loads thereon. A priorqualitative analysis of the native earth material 12 will indicate thetype and degree of stabilization and stabilizer material which must beadded. Amounts of stabilizer material injected through line 76 may bereleased by metering in accordance with stabilization requirementsversus the speed of traverse of mobile support means 44 and 46 along thesurface l4 of earth 12.

While some native soils may require lime additive to bring about properstabilization characteristics, it is contemplated that otherapplications may utilize oil or water or still other compounds asadditives to the native earth material. Proper stabilization having beeneffected, the base layer 34 will be extruded out as a uniform layer withboth base line 36 and surface 38 disposed at a constant distance fromthe external reference or stringline 60. The base layer 34 can then becompacted by following equipment, the uniformity of base layer 34 beingmaintained due tothe initial uniformity of deposition and particle size,whereupon it may be further prepared for additional base material and/ora topmost-paving material to provide the finished roadway.

In cases where native material is unsuitable for base purposes, suchmaterial will have to be imported. Thus, after cutting the roadway baseline to a predetermined base or depth line relative to an externalreference, imported material is deposited in the roadbed for controlleddepth distribution. Native earth material must be completely removedabove the certain prescribed depth line. There is still the assurancethat the bottom of the roadway bed is true and uniform at a preset levelrelative to the grade line.

The controlling discloses a novel method of constructing roadwayswherein native earth material is used to best ad-v vantage constantpavement base support. While the use of native soil is not novel initself, the formation of a native earth material base layer withrequired stabilization as extruded or laid down in uniform thicknessupon a base line which is true to the roadway grade line does constitutenew and useful practice which effects great economy in the building ofimproved quality roads. Economies areenabled not only from savings inhauling, distributing and wastage of nonnative, prepared base materials,but also in job time and man hours per roadway unit distance.

' Changes may be made in the combination and arrangement of steps and/orelements as heretofore set forth in the specification and shown in thedrawings; it being understood that changes may be made in theembodiments disclosed without departing from the spirit and scope of theinvention as it is defined in the following claims.

What I claim is:

l. A method for performing controlled depth stabilization of earthmaterial in situ to form a constant profile layer along a predeterminedroadway path comprising the steps of:

providing a reference line indicating the relative elevation level ofsaid layer;

cutting and comminuting said earth material along said roadway path downto a first level which is disposed a predetermined constant distancefrom said reference line;

simultaneously spreading comminuted earth material approximately evenlyon said roadway to a second level which is disposed a predetermineddistance between said reference line and first level.

2. A method for performing controlled depth stabilization of nativeearth material as set forth in claim I which is further characterized toinclude the step of introducing stabilizing material into said earthmaterial during said cutting and comminuting.

3. A method of performing controlled depth stabilization as set forth inclaim 2 wherein said step of introducing comprises:

spraying stabilizing liquid into said earth material.

4. A method for performing controlled depth stabilization as set forthin claim 2 wherein said step of introducing comprises:

interjecting dry stabilizing material into said earth material.

5. A method of performing controlled depth stabilization as set forth inclaim 3 wherein said stabilizing liquid is oil.

6. A method for performing controlled depth stabilization as set forthin claim 3 wherein said stabilizing liquid is water.

7. A method for performing controlled depth stabilization as set forthin claim 4 wherein said dry stabilizing material is lime.

8. A method for performing controlled depth stabilization as set forthin claim 1 wherein said stop of pro\ iding a reference line comprises:

supporting a stringline at spaced positions along one or both sides ofsaid roadway.

9. A method for performing controlled depth stabilization as set forthin claim 1 which includes the steps of? continuously controllingimplements for cutting and comminuting, and for spreading such that saidsecond level is maintained a constant distance above said first leveland below said reference line.

10. A method for performing controlled depth stabilization as set forthin claim 8 which includes the steps of:

continuously controlling implements for cutting and comminuting, and forspreading such that said second level is maintained a constant distanceabove said first level and below said string line.

H. A method for performing controlled depth stabilization as set forthin claim I which includes the step of:

controlling the rate of said cutting and comminuting of said nativeearth material thereby to limit the average particle size to a selectedstandard.

12. A method for performing controlled depth stabilization as set forthin claim 9 which includes the step of:

controlling the rate of said cutting and comminuting of said nativeearth material thereby to limit the average particle size to a selectedstandard.

13. A method for performing controlled depth stabilization of nativeearth material in situ to form a constant profile layer along apredetermined roadway path comprising the steps of:

providing a reference line indicating the relative elevation level ofsaid layer; cutting and comminuting said native earth material alongsaid roadway path down to a first level which is disposed apredetermined constant distance from said reference line;

simultaneously spreading said comminuted earth material approximatelyevenly on said roadway to a second level which is disposed apredetermined distance between said reference line and first level; and

simultaneously trimming said spread and comminuted earth material atsaid second level which is continually maintained at a preset distanceabove said first level to provide said constant profile layer of thecomminuted native earth material.

1. A method for performing controlled depth stabilization of earthmaterial in situ to form a constant profile layer along a predeterminedroadway path comprising the steps of: providing a reference lineindicating the relative elevation level of said layer; cutting andcomminuting said earth material along said roadway path down to a firstlevel which is disposed a predetermined constant distance from saidreference line; simultaneously spreading comminuted earth materialapproximately evenly on said roadway to a second level which is disposeda predetermined distance between said reference line and first level. 2.A method for performing controlled depth stabilization of native earthmaterial as set forth in claim 1 which is further characterized toinclude the step of: introducing stabilizing material into said earthmaterial during said cutting and comminuting.
 3. A method of performingcontrolled depth stabilization as set forth in claim 2 wherein said stepof introducing comprises: spraying stabilizing liquid into said earthmaterial.
 4. A method for performing controlled depth stabilization asset forth in claim 2 wherein said step of introducing comprises:interjecting dry Stabilizing material into said earth material.
 5. Amethod of performing controlled depth stabilization as set forth inclaim 3 wherein said stabilizing liquid is oil.
 6. A method forperforming controlled depth stabilization as set forth in claim 3wherein said stabilizing liquid is water.
 7. A method for performingcontrolled depth stabilization as set forth in claim 4 wherein said drystabilizing material is lime.
 8. A method for performing controlleddepth stabilization as set forth in claim 1 wherein said step ofproviding a reference line comprises: supporting a stringline at spacedpositions along one or both sides of said roadway.
 9. A method forperforming controlled depth stabilization as set forth in claim 1 whichincludes the steps of: continuously controlling implements for cuttingand comminuting, and for spreading such that said second level ismaintained a constant distance above said first level and below saidreference line.
 10. A method for performing controlled depthstabilization as set forth in claim 8 which includes the steps of:continuously controlling implements for cutting and comminuting, and forspreading such that said second level is maintained a constant distanceabove said first level and below said string line.
 11. A method forperforming controlled depth stabilization as set forth in claim 1 whichincludes the step of: controlling the rate of said cutting andcomminuting of said native earth material thereby to limit the averageparticle size to a selected standard.
 12. A method for performingcontrolled depth stabilization as set forth in claim 9 which includesthe step of: controlling the rate of said cutting and comminuting ofsaid native earth material thereby to limit the average particle size toa selected standard.
 13. A method for performing controlled depthstabilization of native earth material in situ to form a constantprofile layer along a predetermined roadway path comprising the stepsof: providing a reference line indicating the relative elevation levelof said layer; cutting and comminuting said native earth material alongsaid roadway path down to a first level which is disposed apredetermined constant distance from said reference line; simultaneouslyspreading said comminuted earth material approximately evenly on saidroadway to a second level which is disposed a predetermined distancebetween said reference line and first level; and simultaneously trimmingsaid spread and comminuted earth material at said second level which iscontinually maintained at a preset distance above said first level toprovide said constant profile layer of the comminuted native earthmaterial.